Ooh I feel privileged!
Dyson have always measured the suction power of their vacuums at the hose in Airwatts, however I believe that since the EU law for vacuums came in, Dyson started to measure the suction at the cleaner head rather than at the hose and that measurement does look a lot different but it's nothing to worry about at all.
I can also confirm that the Dyson DC41 Mk2 (700w) has 120 AW of suction at the head and 198 AW at the hose. The original old style 1300w DC41 (1300W) has 255 AW of suction at the hose and 160 AW of suction at the cleaner head IIRC.
I have owned both and I would say the DC41 Mk2 crushes the older DC41 hands down. Yes there's less suction but it isn't everything as it's all to do with the head as well as the suction. On the DC41 Mk2 the brushbar motor spins 20% faster , the brushroll has stiffer bristles to agitate the carpet and remove ground in dirt better and there's a max/min slider for normal use and for vacuuming very soiled carpets.
The same thing applies for the DC40 but that has less suction if it's the non EU/ERP model.
Hope this helps